Adjustable scaffold



Feb. 1, 1966 J. R. SMITH ADJUSTABLE SCAFFOLD Filed June 17 4 Sheets-Sheet 1 HUMA/EVS.

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United States Patent 3,232,377 ADJUSTABLE SCAFFLD James R. Smith, Martinsville, Ind., assigner to Baker-Roos, Inc., Indianapolis, Ind., a corporation of Indiana Filed June 17, 1963, Ser. No. 288,182 11 Claims. (Cl. 182--115) This invention relates to adjustable scafolds, and more particularly to that type of scaffold in which an operators platform is supported through vertically extensible means from a portable base structure. It is an object of the invention to produce such a scaffold which will provide a substantialy range of vertical adjustment for the platform and will support the platform stably throughout that range.

A preferred form of adjustable scaffold according to the invention comprises a caster-supported, generally rectangular base frame provided adjacent each of its corners with yan upwardly extending upright or corner post. Rungs extending between the corner posts at one end of Vthe base frame provide a ladder by which a workman may reach a fixed platform supported at or near the tops of the corner posts. The other two corner posts constitute guides slidably receiving the side members of the lower one of two telescopically associated ladder sections, the upper of which carries near its top a second platform, which desirably is arranged for ready attachment to or removal from such upper section. Cross braces, including the aforesaid rungs, extend between and rigidly interconnect the corner posts, whereby the corner posts and base frame form a rigid truck-like structure portably supported on casters. For convenience, that side of such truck-like structure in which the telescopicallyassociated ladder sections are supported will be designated the front, while the opposite side will be designated the rear.

To facilitate extension of the ladder sections they are counterbalanced by a counterweight slidably supported in the truck-like structure. Desirably, the lower ladder section is connected to the counterweight while the upper ladder section is supported from the lower by a cable which runs over a pulley at the top of the lower ladder section and has its ends connected respectively to the trucklike structure and to the bottom of the upper ladder section. Such cable not only functions to carry the weight of the upper ladder section but also serves to coordinate -fold-supporting casters to increase the stability of the scaffold when the ladder sections are extended.

Further objects and features of the invention will become apparent from the following more detailed description and from the accompanying drawings in which:

FIG. l is a perspective View showing a preferred form of scaffold with the ladder sections partially extended;

FIG. 2l is a fragmental plan view of the scaffold with a portion of the lower platform thereof broken away;

FIG. 3 is a vertical section through the lower portion of the scaffold of FIG. 1 with the ladder sections near fully collapsed positions;

FIG. 4 is a horizontal section on the line 4-4 of FIG. 3;

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FIG, 5 is an elevational view of the .inner fa-ce .of one of the front corner posts showing the two telescoping laddersection uprights associated therewith;

FIG. 6 is a horizontal section on the line 6-6 of FIG.

FIG. 7 is a vertical sectional view of the locking means employed to hold the ladder sections extended;

FIG. 8 is an elevational view showing an Outrigger brace in extended position;

FIG. 9 is a horizontal section on the line 9--9 of FIG. 8;

FIG. 10 is a fragmental Vertical section on the line 1tl 10 of FIG. 1;

FIG. 11 is a fragmental elevation showing the adjustable scaffold of FIGS. 1e10 assembled with a prior type of scaffold;

FIG. 11A is a fragmental sectional view taken on the line A-A of FIG. 11; and

FIG. l2 is a fragmental isometric View showing a modified form of counterbalancing means.

The scaffold shown in FIG. 1 comprises a truck-like structure, designated in its entirety by the reference numeral 15, including a generally rectangular base frame 16 to which are attached rear corner posts 17 and front corner posts 18 which extend upwardly from the base frame 16. Horizontal cross-members or rungs 19 extend in vertically spaced relation between the rear corner posts 17 to provide a ladder affording access to a platform 20 located near the uper ends of the corner posts. Cross-members 22 and 23 are secured to and extend between the front corner posts 18, while additional horizontal members 23 extend between and rigidly interconnect the front and rear corner posts. The two front corner posts 18 slidably support a lower ladder section 24 which, in turn, slidably supports an upper ladder section 25.

As shown in FIGS. 5 and 6, the corner posts 18 are conveniently standard channels arranged with their open sides facing toward each other and receiving smaller channels 27 constituting the uprights of the lower ladder section 24, such ladder section also including rungs 28 extending between and secured to the channels 27, desirably near the rear edge thereof. In the upper ladder section 25, uprights 30 are in the form of Z-bars each disposed with its web in a plane perpendicular to the webs of channels 18 and 27. Each of the Z-bars 30 has an outer flange 31 disposed adjacent and parallel to the inner face of the web of the associated upright 27 and an inner flange 32 which projects forwardly beyond and in spaced relation to the edges of the front flanges of the channels 18 and 27. Rungs 33 extend between `and are secured to the inner flanges 32.

To provide for free sliding of the sections 24 and 25 while, at the same time, reducing lost motion, the opposed faces of the several upright members 18, 27 and 30 are provided with rubbing elements. Thus, near the upper end of each corner post 18 a pair of rubbing blocks 35 adapted to engage the flanges of the uprights 27 are secured to the inner faces of the flanges of the corner posts, while a third rubbing block 36 is secured to the inner face of the web of the corner post to engage the web of the upright 27. Near the lower end of each upright 27 a pair of rubbing blocks 37 are secured to the outer faces of the flanges of that upright to bear against the flanges of the corner posts 18, while a third block 3S is secured to the web of the upright 27 to bear against the web of corner post 18. Near the upper end of upright 27 a rubbing block 40 is secured to the forward flange of that upright to bear against the web of upright 30 of the upper ladder section, while a second rubbing block 41 is secured to the web of upright 27 to bear against the outer movement in the truck-like structure.

flange of the upright 30. At the lower end of the upright 30, there is secured to its web a rubbing block 42 adapted to bear against the adjacent flange of the upright 27, while to the outer face of the ange 31 there is secured a rubbing block 43 for engagement with the web of upright 27. In addition, upper and lower rubbing lingers 44 and 45 are secured to the rear flange of the upright 27 and extend forwardly therefrom to bear against the rear face of the web of upright 30. The upper finger 44 is located close to the top of the upright 27, while the lower linger 45 is disposed to engage the lower end of the web 'of upright 30 when the upper ladder section 25 is at its upper limit of movement.

To facilitate extension of the ladder sections 24 and 25, a pair of `Cables 48 secured to the lower end of lower section 24 extend over pulley 49 on the cross-member 23 to a counterweight 50 arranged for generally vertical As shown, the counterweight t) is provided at opposite ends with pairs of rollers 51 running in channel-like guides 52. As will be clear from FIG. 2, the guides 52 extend from the upper horizontal members 23 of the truck-like structure to the base frame 16. Conveniently, the guides 52 are disposed obliquely to extend downwardly and rearwardly from their upper ends. By virtue of this arrangement, that portion of each cable 48 extending between the pulley 49 and the counterweight will be generally parallel to the guide, while the counterweight will be near the rear of the truck-like structure when it is in its lowermost position and the ladder sections fully extended. In order 'that the counterweight may be effective on the upper ladder section 25 as well as on the lower section 24, a

third cable 54 extends from the lower end of the upper ladder section 25 around a pulley 55 at the upper end of the lower ladder section to the cross-member 22 of the truck-,likes structure. The cable 54 not only transfers the weight of the upper ladder section 25 to the lower ladder section 24 but also coordinates the movements of the two ladder sections in such a way that movement of the lower section relative to the corner posts 18 will be accompanied by an equal relative movement of the upper ladder section 25 in the lower section 24.

The counterweight 50 is conveniently constructed as a tank adapted to be filled with sand or other material to provide the mass necessary to balance the combined Iweight of the upper and lower ladder sections 24 and 25.

For the purpose of securing the ladder sections 24 and 25 in any desired position of extension locking devices 56 at the front upper corners of the structure cooperate with a series ofl spaced holes 57 (FIGS. 6 and 7) in the `rear ange of each of the uprights 27 of the lower ladder section 24. Each of such locking devices comprises a sleeve S8, conveniently mounted on the cross-member 23, in which a locking bolt 59 having a reduced end portion 60 is slidably and rotatably received. Each sleeve 58 is provided with a helically extending slot 61, and a locking screw 62 extends through such slot into a transverse screw-threaded opening in the bolt 59. By turning the bolt 59 on its axis, thus causing the screw 62 to traverse' the slot 61, the reduced bolt-end 60 can be advanced into or-retracted from any hole 57 in line with it. By turning the locking screw on its axis its end will be forced against the inner surface of the sleeve 58 to hold the boltend 60 in either advanced or retracted position.

The upper ladder section is adapted to mount an upper platform 65. While such a platform may be sebelt 67 extends through the ears 66 in rear of the rung 33 received between them to retain the platform in association with the upper ladder section 25. The outer or front end of the platform 65 is supported by a pair of tubular braces 68 (FIGS. 1 and 10) the upper ends of which extend through holes in the platform and are provided immediately below the platform with collars 69 on which the platform rests. The lower portions of the braces 68 slope rearwardly and downwardly and terminate in forks 7i) adapted to receive one of the rungs 33 of the upper ladder section.

If desired, the upper platform 65 may be provided with side rails 71 each of which is formed of a length of metal tubing bent into a U-shape to provide a front leg 72 and a rear leg 73. At the lower end of each rear leg 73, such leg is provi-ded with a hook 74 (FIG. 3) adapted to be passed through a slot in the platform 65 and to retain the side rail 71 in association with the platform, with the lower end of the leg 71 resting on the upper surface of the platform. The front legs 72 of the side rails are provided with extension pins 75 receivable in the open upper ends of the brace 68, as shown in FIG. 10. The slots in the platform 65 which receive the hooks 74 extend foreand-aft and are long enough to permit the hooks to be passed through them and the side rails to be moved forwardly to a position in which the pins 75 can be inserted into the upper ends of the braces 68.

To provide stability for the scaffold, the truck-like structure maybe provided with extensible Outrigger braces 77. As will be clear from FIG. 8, each of such outriggers comprises a vertical member 78 rotatably supported at its lower end in a socket 79 mounted on the base frame 16 and spaced forwardly and outwardly from the adjacent corner posts 18. At its upper end, the member 78 is rotatably received in a bracket 80 fixed to the corner post 18. Brace members 81 and 82 secured to the member 7,8 support at their outer ends a vertical tube 83 to the lower end of which a nut 84 is affixed. A screw 85 received in the nut 84 extends upwardly through and beyond the tube 83, where it is provided with ay head 86 by which it may be rotated. A floor-engaging foot 87 is rotatably mounted on the lower end of the screw 85. Y

A link 89 is associated with each Outrigger 77 for the purpose of releasably holding -it in fixed position relative to the structure 15 when the Outrigger is to be used. As shown, each link 89 is provided at one end with a sleeve 90 which receives the tube 83 and is rotatable thereon. At its opposite Vend, the link is provided with a downwardly projecting pin 91 adapted to be received in lany of a plurality of holes 92 provided in the adjacent sides of the base frame 16. The link 89 permits each Outrigger to be locked against rotation in either the full-line or the dotted-line position shown in FIG. 9 or in an other position provided by the holes 92.

When the outriggers are not in use, the screws 85 will be retracted to permit the feet 87 to clear the floor,

, thus permitting each Outrigger to be swung inwardly into overlapping relation at the front of the structure 15. When it is desired to use the outriggers, each is swung into the desired position and locked there by insertion of the pin 91 in the appropriate hole 92, and the screw 85 is rotated to bring the foot 87 into firm engagement with the floor.l

The ladder formed by the rear corner posts 17 and the rungs 19 extending between them may be adapted to serve as one of the ladders of a scaffold of the type shown in United States Letters Patent No. 2,593,122. For this purpose, the uprights 17 are square tubes having, in one or more sides, a series of vertically spaced openings 95 adapted to receive spaced lugs provided on an inner face of an angle-iron guide 96 forming part of a side-rail structure 97 adapted to support a platform 98, all as more fully set forth in said prior Patent No. 2,593,122. In addition, each of the uprights 17 may be provided at its upper end with an upwardly projecting pin 99 adapted to be received in a socket provided to the lower end of each upright of a superposed ladder, again as fully shown in said Patent 2,593,122.

In FIG. 12 is shown a modified form of means for counter-balancing the weight of the two ladder sections 24 and 25. This arrangement is especially advantageous when the available room for vertical movement of the counterweight 50 arranged as in FIGS. 1 4 is insufiicient to accommodate complete extension of the ladder sections. In the arrangement of FIG. 12, the counterbalancing cables 48 extend from the lower end of the lower ladder section 24 over the pulleys 49 as before; but instead of being directly connected to the counterweight 50 they are secured to and wound on drums 100 fixed on a transverse shaft 101 rotatably supported in the truck-like structure 15. Also fixed to the shaft 101 are a pair of smaller drums 102 on which are wound cables 103 supporting the counterweight 50, which is guided for vertical movement by guides 104 forming a part of the structure 15. Because of the difference Vbetween the diameter of the drums 100 and the diameter of the drums 102, the vertical movement of the counterweight 50 may be made substantially less than the vertical movement of the lower ladder section 24. As in the arrangement of FIGS. 1 4, the weight ofthe upper ladder-section is transferred to the lower section through the cable 54.

While the scaffold illustrated can be made in any desired dimensions, a scaffold having wide application, especially for use within buildings, has such a size that it may be passed through ordinary doorways when collapsed. For such use the scaffold may have an over-all width of 30 inches or slightly less and a height of approximately 61/2 feet over the fully retracted ladder sections. Such a height perimts the ladder sections to be extended until the upper end of the upper section 2S is approximately 15 feet from the floor while still providing adequate overlapping of the lower section on both the upper section and the front uprights 18.

The scaffold is most conveniently operated from the lower platform 20, access to which is readily gained via the ladder 17-19. Standing on the platform 20, an operator can readily operate the locking devices 56 and, by applying vertical effort to either of the ladder sections, extend or retract them as desired. When the ladder sections are near their retracted positions, it will usually be most convenient for the operator to apply the lifting effort to the upper section 25. However, when the ladder sections are near fully extended positions, it will probably be more convenient for the vertical effort to be applied to the lower section 24, since application of the effort to the upper section might require the operator to reach through the spaces between the rungs of the lower section. It is the interconnection of the ladder sections by the cable 54, coupled with the counterbalancing of both sections by the single counterweight, that makes it possible to effect movement of both sections by an effort applied to either.

When the ladder sections are extended or retracted to the desired height, the locking devices are operated to advance the bolt-end 60 of each into an aligned hole 57 in the adjacent upright 27 of the lower ladder section, whereupon the screws 62 may be tightened to prevent accidental retraction of the bolt-ends. If desired, the outer ange 31 of each upright 30 of the upper ladder section may be provided with a series of holes 106 for the reception of a bolt or pin adapted to engage the upper end of the associated upright 27 of the lower ladder section 24 to prevent descent of the upper ladder section in event of failure of the cable 54.

I claim as my invention:

1. An extensible scaffold, comprising a portable base structure, upper and lower telescopically associated ladder sections, vertically extending guide means at the front of said base structure guiding the lower ladder section for vertical movement, a pulley carried by said lower ladder section near the upper end thereof, a flexible cable having an intermediate portion running over said pulley and end portions extending downwardly therefrom and secured respectively to said base structure and to the upper ladder section near the lower end thereof whereby vertical movement of the lower ladder section in said guide means will be accompanied by a substantially equal movement of the upper ladder section in the lower, counterbalancing means [for in large part counterbalancing the combined weight of said two ladder sections, said counterbalancing means including a counterweight operatively connected to the lower ladder section and guided for generally vertical movement in said base structure, whereby both said ladder sections will be extended and retracted in response to manual effort applied to either ladder section, and releasable locking means for locking said' ladder sections in selected elevated positions.

2. A scaffold as set forth in claim 1 with the addition that said counterbalancing means includes a second pulley mounted near the top of the base structure at the front thereof, counterweight guiding means extending obliquely downwardly and rearwardly from a point below said second pulley, and a second fiexible cable extending from the counterweight, over the second pulley, to the lower ladder section adjacent t-he lower end thereof.

3. A scaffold as set forth in claim 1 with the addition that said counterbalancing means includes a second pulley mounted near the top of the base structure at the front thereof, a pair of coaxial drums of different diameter carried within the confines of said base structure and arranged for rotation as a unit about their common axis, a second cable wound on the larger drum and extending therefrom over said second pulley and thence to the lower ladder section adjacent the lower end thereof, and a third cable wound on the smaller drum and connected to the counterweight.

4. A scaffold as set forth in claim 1 in which said releasable locking means acts between the base structure and the lower ladder section for locking such section in fixed position relative to said guide means.

5. A scaffold as set forth in claim 4 with the addition that said lower ladder section comprises a vertically extending member provided with a series of vertically spaced holes, said locking means comprising a bolt mounted on the base structure for movement into and out of any of said holes.

6. An extensible scaffold, comprising a portable base structure, upper and lower telescopically associated ladder sections, vertically extending guide means at the front of said base structure guiding the lower ladder section for vertical movement, said guide means comprising a pair of posts of channel cross-section disposed in spaced parallel relation with their open sides directed toward each other, said lower ladder section having a pair of channel-section uprights nested and slidable in said posts and likewise disposed with their open faces directed toward each other, vertically spaced rungs abutting and joined to the webs of said uprights and rigidly interconnecting said uprights, said upper ladder section having a -pair of Z-bar uprights slidably received in said channelsection uprights and located in front of said rungs, each Z-bar upright being disposed in its associated channelsection upright with its web perpendicular to the web of the associated channel-section upright, with one flange extending rearwardly from the web toward said rungs close to the web of the channel-section upright, and with the other ange projecting forwardly, and vertically spaced rungs extending between and rigidly secured to the last named flange o-f each Z-bar upright.

7. A scaffold as set forth in claim 6 with the addition that each of said posts is provided near its top with rubbing elements of limited vertical extent engageable with the outer surfaces of the web and flanges of the associated channel-section upright, each of said channel-section uprights being provided near its lower end with rubbing elements of limited vertical extentengageable with the inf ner faces of the web and flanges of the associated post and near its upper end with rubbing elements engaging the outer face of the rst named ange and opposite faces of the web of the associated Z-bar upright, each channelsection upright being provided intermediate its length with an additional rubbing element engageable with the rear face of the web of thevassociated Z-bar upright, eachZ- bar upright being provided near its lower end with rubbing elements engageable with the inner faces of the web and front ange of the associated channel-section upright.

8. In an extensible scatold, upper and lower telescopically associatedladder sections, said lower section comprising a pair of parallel uprights of channel section disposed with their open sides directed toward each other, horizontal rungs extending between and secured to said uprights, the ends of said rungs being located between the flanges of the uprights, said upper section comprising a pair of uprights of yZ-bar cross-section slidably received respectively in the uprights of the lower section, each of said Z-bar uprights having a webV disposed parallel and close to one flange of the associated lower-section upright, a rst flange lying parallel and close to the web of such lower section upright and projecting from the Z-bar web toward said rungs, and a second flange projecting from said web beyond sai-d one ange of the associated lowersection upright, and rungs extending between and secured to the Z-bar uprights. l

9. A scaffold as set forth in claim 8 with the addition that the ends `of the last named rungs abut against the second Z-bar flanges.

10. An extensible scaiold, comprising a generally rectangular base frame, a pair of front corner posts and a pair of rear corner posts extending upwardly from said base frame, a platform supported by said corner posts above said base frame, a ladder section supported by said front corner posts for vertical sliding movement, counter balancing means mounted Vwithin the contines of said base lframe and below said platform and connected for-counter balancing said ladder section, rungs extending between said rear corner posts, and means operable from said platform for locking said ladder section at a desired elevation.

11. An extensible scaold, comprising a generally rectangular base frame, a pair of front corner posts and a pair of rear corner posts extending upwardly from said base frame, a platform supported by said corner posts above said base frame, a ladder section supported by said front corner posts for vertical sliding movement, counter balancing means mounted within the confines of said base frame and below said platform and connected for counter balancing said ladder section, rungs extending between said rear corner posts, each of said rear corner posts being provided with a series of vertically spaced openings, a second platform, members supporting said second platform, each of said members having vertically spaced lugs receivable in said openings.

References Cited bythe Examiner UNITED STATES PATENTS 252,966 1/1882 Pierce 187-94 399,313 3/1889 Bradford 182-208 487,039 11/1892 Volz 187-9 1,192,387 7/1916 Cardarelli 182-67 2,335,046 11/1943 Droeger 182-119 2,593,122 4/ 1952 Droeger 182-180 2,787,343 4/ 1957 Mitchell 182-'63 2,923,373 2/1960 Ledgerwood 182-195 2,961,060 11/1960 Taylor 182-'102 3,020,972 2/ 1962 Hockett 182--127 FOREIGN PATENTS 92,731 10/ 1958 Norway.

HARRISON R. MOSELEY, Primary Examiner.

REINALDO P. MACHADO, Examiner. 

11. AN EXTENSIBLE SCAFFOLD, COMPRISING A GENERALLY RECTANGULAR BASE FRAME, A PAIR OF FRONT CORNER POSTS AND A PAIR OF REAR CORNER POSTS EXTENDING UPWARDLY FROM SAID BASE FRAME, A PLATFORM SUPPORTED BY SAID CORNER POSTS ABOVE SAID BASE FRAME, A LATTER SECTION SUPPORTED BY SAID FRONT CORNER POSTS FOR VERTICAL SLIDING MOVEMENT, COUNTER BALANCING MEANS MOUNTED WITHIN THE CONFINES OF SAID BASE FRAME AND BELOW SAID PLATFORM AND CONNECTED FOR COUNTER BALANCING SAID LADDER SECTION, RUNGS EXTENDING BETWEEN SAID REAR CORNER POSTS, EACH OF SAID REAR CORNER POSTS BEING PROVIDED WITH A SERIES OF VERTICALLY SPACED OPENINGS, A SECOND PLATFORM, MEMBERS SUPPORTING SAID SECOND PLATFORM, EACH OF SAID MEMBERS HAVING VERTICALLY SPACED LUGS RECEIVABLE IN SAID OPENINGS. 